GIF vs JPG

When you are saving images, either from a scanned image, or from a screen shot, which type of file should you save it as? GIF, JPG or other?

GIF

Gifs are good for images with large blocks of colour such as screen shots, clipart etc. Lines and borders remain sharp, but the number of colours in the picture is limited to 256, generally too few for photos but plenty for documents. The following image is one you would use the GIF format for:

JPG

JPG (or JPEG) images should be used to save photos or images with lots of colour gradients. JPG compression is "lossy" which means saving the image as a JPG will lose some of the picture quality. JPG compression works by dividing the image into zones and discarding subtle colour differences. The higher the compression the smaller the file size, but also the more photo information that will be lost. If you try to save a line-art image as a JPG you will not only lose quality but the file size will be larger than GIF. The following image is one you would use the JPG format for:

GIF vs. JPG quick comparison

• Use GIF files for line art, text, screen shots etc
• Use JPG files for photos and images with many gradients

Other formats

There are other image file formats in use, many of which are specific to the program that created them. One format of note in web design is PNG. PNG is a format similar to GIF, but usually has a smaller file size and supports more than 256 colours. The main downside of PNG compared to GIF is that very old web browsers (eg. Internet Explorer 3) will not display PNG images.
`

More information

More information on image file formats can be found on this Wikipedia page